What skinwalker and Altena said. Here're my thoughts on it OP.

When I play an RPG, I make one character and only one character. This allows me to pour myself into that character, which makes me feel connected to both the game and the character itself. In games where I'm forced to play as only one class, I'm then forced to only play as one character, because the second I make an alt, I lose all connection to the game. It then becomes a game of "How many alts can you make." See GW2 for an example of this. In that game, once you've chosen your class, you're locked to it.

I completely disagree that being locked to one job is an inherent Final Fantasy trait as well as being something necessary for enjoyment. It seems like it's a trait you picked from a couple of past Final Fantasy games, but it's certainly not the standard, especially considering there's no real standard among the series to begin with. In the Final Fantasy Tactics games, you're allowed to freely change between classes and jobs whenever you feel like, and even though it may not have as rich a character roster as the rpg games, they still were an absolute blast to play simply because your team was truly yours; all the skills they know and weapons they used were because you made it that way.

In short, forcing us to play as a single class is easily one of the quickest ways to alienate a big part of the playerbase. It's a relic feature that really has no place in FFXIV. Locking us to one class in Yoshi's amusement park would turn the game from something grand into just another throwaway MMO, like GW2 or TERA.